JP5252617B2 - Method for producing film-like carbon material and film-like carbon material - Google Patents

Description

  The present invention relates to a method for producing a film-like carbon material using a polyacetylene film.

  Carbon materials have applications in a wide range of fields, such as electrode materials for various batteries, image materials such as flat-screen televisions, conductive materials, and composite materials. Above all, film-like carbon composed of aggregated carbon fibrils with an average fiber diameter of nanometer level has a structure showing high conductivity in the direction in which the carbon nanofibrils are oriented, so the current direction is controlled in a unique direction. Therefore, new applications are expected in the energy field, the electronics field, and the like. For the purpose of producing film-like carbon having such a unique structure, the inventor, as shown in the following patent document, is a polyacetylene film formed by agglomerating fibrils having an average fiber diameter of nanometer level As a precursor, we have attempted to study film-like carbon formed by agglomerating graphitized carbon fibrils having an average fiber diameter of nanometer level maintaining the shape of the precursor by carbonizing at high temperature.

  For example, in Japanese Patent Application Laid-Open No. 2004-115354 (Patent Document 1), polyacetylene (see FIG. 1 of Patent Document 1) in which a solid structure is controlled in a specific form (spiral shape) is used as a precursor substance, and a temperature of 500 ° C. A technique for producing a nanometer-sized graphite-like substance (see FIG. 2 of Patent Document 1) by performing heat treatment (carbonization) at a temperature of 1800 ° C. is disclosed.

  Japanese Patent Laid-Open No. 2004-269337 (Patent Document 2) discloses a technique for producing a nanometer-sized graphite-like substance by heat-treating polyacetylene at a temperature of 500 ° C. to 1800 ° C. in the presence of a metal catalyst. Is disclosed.

Although not a technique studied by the inventor, Japanese Patent Application Laid-Open No. 57-153037 (table of Patent Document 3) discloses that heat treatment is performed on polyacetylene doped with an electron acceptor at a temperature of 650 ° C. to 760 ° C. Discloses a technique for producing conductive polyacetylene.
Japanese Patent Laid-Open No. 2004-115354 FIGS. 1 and 2 JP 2004-269337 A JP-A-57-153037 Table

  However, as shown in Patent Document 1, film-like carbon that maintains the shape of the precursor of polyacetylene when viewed at the nanometer level cannot be obtained by merely heat-treating (carbonizing) the polyacetylene film (patented) The carbon obtained by macroscopically seeing FIG.1 and FIG.2 of the literature 1 is not a film form. This is because the polyacetylene film is carbonized in an inert gas atmosphere, but the precursor polyacetylene film undergoes thermal decomposition, low molecular weight, gasification, etc. during the heat treatment process for carbonization. This is considered to be due to the decrease in the weight and the fragmentation and granulation (see FIG. 13 of the present invention).

  In addition, as shown in FIG. 1 of Patent Document 2, even when polyacetylene is heat-treated (carbonized) under a metal catalyst, the shape of the precursor is maintained when viewed at the nanometer level as in the technique of Patent Document 1. The film-like carbon to be obtained cannot be obtained (see FIG. 1 of Patent Document 2), and the carbon obtained by macroscopic observation is not in a film shape.

  In addition, since the technique of patent document 3 aims at manufacture of electroconductive polyacetylene (because it does not aim at carbonization), since the temperature of the heat processing actually performed is as low as 650-760 degreeC, In the technique of Patent Document 3, although a part of polyacetylene can be carbonized, it cannot be graphitized. Therefore, even if the technique of Patent Document 3 is used, it is impossible to obtain a film-like carbon material made of graphitized fibrils having an average fiber diameter of nanometer size, which is the object of the present invention. Incidentally, the table (Example 7) of Patent Document 3 describes that polyacetylene decomposes when heat-treated at a temperature of 820 ° C., and graphitized film-like carbon using the technique of Patent Document 3 as well. It is clear that is not formed.

  An object of the present invention is to provide a fibril having an average fiber diameter of nanometer level that maintains the shape of the precursor as it is when carbonized as a precursor of a polyacetylene film constituted by aggregation of fibrils having an average fiber diameter of nanometer level. The object is to obtain a film-like carbon material constituted by agglomeration of carbon fibrils having a maintained structure.

  In the method of the present invention, a polyacetylene film is doped with iodine, and the iodine-doped polyacetylene film is used as a precursor, and carbonized in an inert gas atmosphere to maintain the shape of the nanometer level average fiber. This is a method for producing a film-like carbon material constituted by aggregation of graphitized carbon fibrils having a diameter.

  In the present invention, as the polyacetylene film, a polyacetylene having a film shape formed by agglomerating fibrils having an average fiber diameter of nanometer level is used. Here, the “average fiber diameter” means that the diameter of a predetermined number of fibers in the fibrous tissue constituting the fibril structure is measured by a scanning electron microscope (SEM) or the like, and the number averages them. Means the value obtained. The structure in which fibrils having an average fiber diameter on the nanometer level are aggregated includes a structure in which fibrils having an average fiber diameter on the order of nanometers are aggregated in a specific direction, or fibrils are concentrically wound in a spiral shape. Some have a structure in which many portions are aggregated. In addition, the part formed by concentrically winding in a spiral shape may have a large number of circular structures having a diameter of the spiral aggregate structure of less than a micron. In the present invention, a polyacetylene film having an average fiber diameter of 100 to 200 nanometers can be used as the polyacetylene film having an average fiber diameter of nanometer level.

In the present invention, iodine, which is an electron acceptor, is used as a dopant for doping the polyacetylene film. Iodine (I ₂ ) is a halogen molecule and acts as an electron acceptor that receives electrons when doped into a polyacetylene film. Further, iodine bromide may be used in place of iodine as a dopant for the polyacetylene film. Iodine bromide (IBr) is an interhalogen compound and, like iodine, acts as an electron acceptor that receives electrons when doped in a polyacetylene film. The doping condition of iodine bromide to polyacetylene is the same as that in the case of iodine, or it is better that the doping time is shorter at the same temperature.

  The heat treatment temperature for carbonizing the precursor is preferably heat treatment at a temperature in the range of 1000 ° C to 2500 ° C. When the heat treatment temperature is lower than 1000 ° C. (for example, the heat treatment temperature is in the range of 500 ° C. to 1000 ° C.), it can be carbonized but is structurally amorphous (not graphitized). Further, when the heat treatment temperature is higher than 2500 ° C., the state of carbonization and crystallization does not change so much. In contrast, when the heat treatment temperature is in the range of 1000 ° C. to 2500 ° C. as in the present invention, graphitization proceeds as a whole with an increase in the heat treatment temperature, and a better crystalline state is obtained.

  Note that argon gas is used as the inert gas used in the step of heat-treating the precursor.

  In the present invention, as a method of doping an electron acceptor such as iodine in a polyacetylene film, a general known method (for example, H. Shirakawa et al. , J. Chem. Sci. Chem. Comm., Pp 578-580 (1977), etc.) can be used. The doping of the electron acceptor as a dopant may be carried out in air if the conjugated polymer doping the electron acceptor is chemically stable in air, but the conjugated polymer is chemically in air. When unstable, it is desirable to carry out in an inert gas atmosphere. Therefore, in the present invention using a polyacetylene film that is chemically unstable in air, the electron acceptor is doped in an inert gas atmosphere.

  When the electron acceptor is iodine, the electron acceptor may be doped by simply contacting the polyacetylene film with iodine gas at normal temperature and pressure. For example, the polyacetylene film is exposed to gaseous iodine for 0.5 hour or more in an inert gas atmosphere at a temperature near room temperature and under atmospheric pressure. In this case, the gas pressure of iodine may be the vapor pressure of iodine near room temperature at normal pressure. Thus, the precursor of the polyacetylene film doped with iodine as an electron acceptor becomes a film-shaped precursor constituted by agglomeration of polymer fibrils having dimensions on the nanometer level. Further, when iodine bromide is used as a dopant instead of iodine, the room temperature and normal pressure may be used as in the case of using the above-mentioned iodine, but the doping time is shorter than that of iodine. % Time is sufficient.

Here, the mechanism of carbonization when a polyacetylene film is doped with iodine as an electron acceptor will be described. First, it is known that a charge transfer complex is formed between iodine ions (I ₃ ⁻ and I ₅ ⁻ ) and a polyacetylene molecule (for example, S. Roth et al., Advances in Physics, Vol. 36, pp 385-462 (1987)). That is, when polyacetylene is doped with iodine, holes are generated in the polyacetylene molecules, and the generation of the holes causes high conductivity in the polyacetylene molecules. Under such conditions, when the polyacetylene molecule doped with iodine is heat-treated (carbonized) at a high temperature, the charge transfer complex between the iodine and the polyacetylene molecule causes a chemical reaction at a high temperature. Specifically, by removing hydrogen from the polyacetylene molecule and generating hydrogen iodide (HI), it is considered that the carbon generated from the polyacetylene is condensed and changed into a carbon material having a network structure of 6-membered ring carbon. . Since this reaction is a solid-phase reaction, the fibril shape with an average fiber diameter of the precursor and the tissue structure formed by aggregation of the fibrils (that is, all structures of the precursor) are carbon as they are. It is maintained after conversion. As a result, the macroscopic-sized film-like precursor becomes a macroscopic-sized film-like carbon material as it is.

  In the method for producing a film-like carbon material of the present invention, iodine or iodine bromide is used as an electron acceptor in a polyacetylene film (film-shaped polyacetylene) without performing the heat treatment step at a heat treatment temperature of 1000 ° C. to 2500 ° C. After the step of doping, a carbon material having a film shape constituted by agglomeration of carbon fibrils having an average fiber diameter of nanometer level maintaining the shape of a precursor of polyacetylene film doped with iodine or iodine bromide, By reheating the film-shaped carbon material, a film-shaped carbon material constituted by agglomeration of graphitized carbon fibrils having an average fiber diameter of nanometer level maintaining the shape of the precursor may be produced. . By performing such a reheat treatment, it can be reliably graphitized.

  In the process of making a carbon material in the form of a film before re-heat treatment, a precursor is obtained by heat treatment at a heat treatment temperature of 500 ° C. or more in an inert gas atmosphere using a polyacetylene film doped with iodine or iodine bromide as a precursor. Is carbonized. At this point, it has not been completely graphitized. Here, the heat treatment temperature of 500 ° C. or higher means that the heat treatment temperature may be a sufficient temperature at which carbonization is performed by the heat treatment. Therefore, the actual heat treatment temperature is preferably in the range of 500 ° C to 1000 ° C. More preferably, the range of 700 ° C to 900 ° C is good. In addition, when heat processing temperature is lower than 500 degreeC, dehydrogenation is inadequate and it does not progress to sufficient carbonization.

  Next, in the step of re-heat-treating the film-shaped carbon material, the film-shaped carbon material heat-treated and carbonized in the step of forming the film-shaped carbon material is returned to room temperature and then re-heat-treated. The temperature of the reheat treatment is preferably 2000 ° C. to 3000 ° C. When the reheat treatment temperature is lower than 2000 ° C., it is not completely graphitized, and when the reheat treatment temperature is higher than 3000 ° C., it is difficult on the heat treatment apparatus.

  When such a method of re-heat treatment is used, first, in the step of producing a film-shaped carbon material (heat treatment temperature is in the range of 500 ° C. to 1000 ° C.), it is only carbonized and is structurally amorphous. In the re-heat treatment step, the re-heat treatment temperature is 2000 ° C. and a graphitized crystal state is obtained. When the reheat treatment temperature is around 2500 ° C. to 3000 ° C., the progress of crystallization of nanometer size is almost stopped, and the entire crystal state becomes the highest.

  The heat treatment or reheat treatment time at each of the above temperatures is preferably in the range of about 15 minutes to 1 hour.

  As described above, when the method for producing the film-like carbon material of the present invention is used, when the polyacetylene film formed by agglomerating fibrils having an average fiber diameter of nanometer level is carbonized as a precursor, the shape of the precursor is changed. It is possible to obtain a film-like carbon material constituted by agglomerating carbon fibrils maintaining a fibril structure having an average fiber diameter of nanometer level maintained as it is.

  The film-like carbon material of the present invention can be produced by the above-described method for producing the film-like carbon material of the present invention. The film-like carbon material of the present invention is carbonized using a polyacetylene film formed by agglomerating fibrils having an average fiber diameter of nanometer level as a raw material, and graphitized carbon fibrils while maintaining the shape of the fibrils. It is a film-like carbon material constituted by aggregation. Such a film-like carbon material exhibits high conductivity in the direction in which the carbon nanofibrils are oriented, and a direction perpendicular thereto exhibits low conductivity. May be controlled in a specific direction, or a magnetic field may be generated.

  According to the present invention, when a polyacetylene film having a shape formed by agglomerating fibrils having an average fiber diameter of nanometer level is carbonized, the nanometer size of the polyacetylene film substantially maintaining the shape in which the fibrils are aggregated. A film-like carbon material constituted by agglomeration of graphitized carbon fibrils can be produced.

  Hereinafter, an example of an embodiment of a method for producing a film-like carbon material of the present invention will be described with reference to the drawings as appropriate. In the embodiment of the present invention, first, a step of doping an electron acceptor into a film-shaped polyacetylene (polyacetylene film) is performed. In this example, a helical polyacetylene film is used as the polyacetylene film. FIG. 1 is a structural formula of polyacetylene constituting the polyacetylene film used in the embodiment of the present invention. As shown in FIGS. 2 to 6, the polyacetylene film is formed by agglomerating fibrils having an average fiber diameter of nanometer level. The average fiber diameter of the polyacetylene film used in the present embodiment is 100 to 200 nanometers. In this example, with a scanning electron microscope (SEM), the diameters of 100 or more fibers in the fibrous tissue constituting the fibril structure are measured, and a value obtained by number averaging them is obtained. Average fiber diameter. FIG. 2A is a photograph of a part of polyacetylene chiral nematic liquid crystal (N * -LC) taken at 140 × with a polarizing microscope, and FIG. 2B is a chiral nematic liquid crystal (FIG. 2A) ( It is the photograph which image | photographed 240 times of the chiral nematic liquid crystal reaction field constructed | assembled based on (N * -LC) with the scanning electron microscope (SEM). FIG. 3A is a photograph of the domain structure of the helical polyacetylene film synthesized in the chiral nematic liquid crystal reaction field of FIG. 2B taken at 250 times by SEM, and FIG. ) Is a photograph of a part of the domain structure of the helical polyacetylene film taken by SEM at 15000 times. Further, FIG. 4 is a photograph of a part of the domain structure of the horizontally oriented polyacetylene film taken by SEM at 20000 times. FIG. 5 is a photograph of a part of the domain structure of the vertical alignment type polyacetylene film taken at 20000 times by SEM. FIG. 6 is a photograph of a part of the domain structure of the oriented helical polyacetylene film taken by SEM at a magnification of 5000 times.

In the present embodiment, first, a polyacetylene film having a tissue structure formed by aggregating a large number of fibrils having an average fiber diameter of nanometer size was synthesized from the polyacetylene shown in FIG. Such a polyacetylene film was specifically synthesized by the following procedure. First, an equimolar mixed nematic liquid crystal (N-LC) of phenyl cyclohexyl (PCH) liquid crystal PCH302 and PCH304, which is stable against a polymerization catalyst Ti (On-Bu) ₄ -AlEt ₃ (Ziegler-Natta catalyst) (R) -or (S)-(PCH506) ₂ -Binol, which is an axial chiral binaphthyl derivative having a liquid crystal group disubstituted, is added as a chiral dopant to form a chiral nematic liquid crystal shown in FIG. N * -LC). Then, a polymerization catalyst was added to the prepared liquid crystal solvent to construct an asymmetric liquid crystal reaction field shown in FIG. An acetylene gas (99.9999%) was introduced into the reaction field at room temperature or lower (10 to 15 ° C.) at a predetermined pressure (10 to 100 Torr) to synthesize a helical polyacetylene film shown in FIG. . The film thickness of the synthesized helical polyacetylene film was about 1 to 5 μm.

  In this embodiment, a helical polyacetylene film is used as the polyacetylene film, but other polyacetylene films (horizontal alignment type polyacetylene film, vertical alignment type polyacetylene film and alignment helical type polyacetylene film shown in FIGS. 4 to 6 are used. Of course, a polyacetylene film other than the helical type polyacetylene film (such as the polyacetylene film shown in FIGS. 4 to 6) does not show any particular conditions, but the polyacetylene fibrils aggregate. It can synthesize | combine by controlling suitably the conditions to perform.

  Next, a heat treatment is performed in an inert gas atmosphere using a polyacetylene film doped with an electron acceptor as a dopant as a precursor. In the present embodiment, a helical polyacetylene film synthesized as described above was used as the polyacetylene film, and iodine was doped into this. Iodine doping was carried out for 10 hours in a sealed container at room temperature in an oxygen-free argon atmosphere (melting point of iodine, 114 ° C., vapor pressure 0.31 mmHg). The reason why it is performed in a closed container under an oxygen-free argon atmosphere is to prevent oxidation because the polyacetylene film is unstable in air. Iodine was doped as gaseous iodine which was put in a closed container and vaporized by sublimation of solid iodine. Gaseous iodine can easily be doped at room temperature because it easily receives electrons and becomes ions. In this example, iodine is doped at room temperature. However, in order to increase the doping speed, doping may be performed at a temperature higher than room temperature.

  In the present embodiment, the doping amount of iodine doped into the helical polyacetylene film was controlled so that the molar ratio of the helical polyacetylene film and iodine was 1: 0.25. The doping amount of iodine in which the molar ratio of the helical polyacetylene film and iodine is 1: 0.25 is included in a stoichiometric range. When iodine is doped under such conditions, the carbon yield of the helical polyacetylene film is high, and the film-like carbon that retains the nanometer-sized fibril structure of polyacetylene while maintaining the shape of the film as it is. Material can be obtained.

  Note that when iodine bromide is used as a dopant instead of iodine, as in the case of doping iodine described above, in an oxygen-free argon atmosphere at room temperature (since iodine bromide has a melting point of about 40 ° C., room temperature It was carried out in a closed container (which is easy to vaporize in the vicinity). In this case, the doping time is 10 minutes.

  Next, heat treatment was carried out in the following manner until the helical polyacetylene film was carbonized using a helical polyacetylene film doped with iodine as a precursor. First, the synthesized helical polyacetylene film is sandwiched between nickel foil (thickness 0.1 mm) or carbon plate (thickness 2 mm), and is heated for 1 hour at 800 ° C. in an argon gas atmosphere using a vacuum electric furnace. Heat treatment was performed at a rate of 10 ° C./min. The structure of the film-like carbon material obtained by the heat treatment was observed using a scanning electron microscope (SEM). FIG. 7A is a photograph of a part of the domain structure of a film-like carbon material obtained by heat-treating a polyacetylene film doped with iodine according to an embodiment of the present invention at 800 ° C. at a magnification of 10,000 times with an SEM. FIG. 7B is a photograph of a part of the domain structure of the film-like carbon material shown in FIG. By SEM observation using these photographs, the shape of the carbon fibrils in the film-like carbon material obtained by heat treatment at 800 ° C. is almost completely maintained as the shape of the fibrils in the helical polyacetylene film before the heat treatment. Yes. That is, according to the present embodiment, it was confirmed that a film-like carbon material having a highly controlled nanometer-sized tissue structure can be produced.

  The film-like carbon material obtained by the heat treatment at 800 ° C. was graphitized by further heat treatment at 2600 ° C. for 1 hour (at a heating rate of 20 ° C./min) in an argon gas atmosphere using a vacuum electric furnace. The structure of the film-like carbon material obtained by graphitization was observed using a scanning electron microscope (SEM) and a transmission electron microscope (TEM). FIG. 8 (A) is a photograph obtained by photographing the domain structure of the film-like carbon material obtained by further heat-treating the film-like carbon material of FIG. 7 (A) at 2600 ° C. with an SEM at a magnification of 1500 times. ) Is an enlarged photograph of the domain structure of the film-like carbon material of FIG. Even when heat-treated at 2600 ° C. and graphitized by SEM observation using these photographs, the shape of the obtained film-like carbon material is almost completely the shape of the fibril constituting the helical polyacetylene film before the heat treatment. Is maintained. Thereby, it was confirmed that a film-like carbon material having a highly controlled nanometer-sized tissue structure can be graphitized.

  In this example, the film-like carbon material obtained by carbonization at 800 ° C. is once cooled at room temperature, and the film-like carbon material is further heat-treated at 2600 ° C. to be graphitized to form a film-like carbon material (graphite However, the film-like carbon material obtained by carbonization at 800 ° C. may be continuously reheated as it is and graphitized at 2600 ° C.

  FIG. 9 shows a part of the domain structure of a film-like carbon material obtained by heat-treating a polyacetylene film doped with iodine bromide according to another embodiment of the present invention at 800 ° C. at a magnification of 5000 times by SEM. It is a photograph. As shown in FIG. 9, even when iodine bromide is doped, the shape of the carbon fibril in the film-like carbon material obtained by heat treatment at 800 ° C. is the shape of the fibril in the helical polyacetylene film before the heat treatment. Is almost completely maintained. Thus, it was confirmed that a film-like carbon material having a highly controlled nanometer-sized tissue structure can also be produced by doping iodine bromide instead of iodine. Note that in this specification, an SEM photograph in which a film-like carbon material obtained by doping with iodine bromide and heat-treating at 800 ° C. is re-heated (a photograph in the case of re-heat-treating at 2600 ° C. corresponding to FIG. 8). ) Is not specifically shown, but the shape of the obtained film-like carbon material maintains the shape of the fibril constituting the helical polyacetylene film before the heat treatment almost completely even when re-heat-treated at 2600 ° C for graphitization. Make sure you do. Accordingly, even when iodine bromide is doped instead of iodine, a film-like carbon material having a highly controlled nanometer-sized tissue structure can be graphitized. Also, in the case of doping with iodine bromide instead of iodine, the film-like carbon material obtained by carbonization at 800 ° C. may be once cooled at room temperature and reheated at 2600 ° C. for graphitization. The film-like carbon material obtained by carbonization at 800 ° C. may be continuously heated again as it is and graphitized at 2600 ° C.

  Here, the effect of chemical doping in the heat treatment of the helical polyacetylene film doped with iodine in this embodiment was examined by differential thermal analysis (DTA / TG). FIG. 10 (A) is a graph showing the results of analyzing the polyacetylene film before doping with iodine by differential thermal analysis (0 ° C. to 1000 ° C.), and FIG. 10 (B) shows the polyacetylene film after doping with iodine. It is a graph which shows the result analyzed by the differential thermal analysis (0 degreeC-1000 degreeC). As a result of examining these graphs, the disappearance of a peak corresponding to intermolecular crosslinking and thermal decomposition (DTA peak near 300 ° C. to 500 ° C.) was observed by doping with iodine. This is thought to be due to the disappearance of thermal decomposition and gasification of the helical polyacetylene film, and the formation of a film-like carbon material (including graphite) that highly maintains the structure of the helical polyacetylene that is the object of this embodiment. It is thought to support Furthermore, from this differential thermal analysis, the weight loss of the helical polyacetylene due to the heat treatment can be made very small by doping with iodine. This result is considered to indicate that the carbon yield is high. It turned out that the film-form carbon material which processed the helical polyacetylene film after iodine doping actually at 800 degreeC and 2600 degreeC is obtained with a film form with a high carbon yield (70-80%). In addition, these film-like carbon materials completely retained the domain structure and helical structure of helical polyacetylene.

  Similarly, in another embodiment of the present invention, the effect of chemical doping in the heat treatment of a helical polyacetylene film doped with iodine bromide was also examined by differential thermal analysis (DTA / TG). FIG. 11 is a graph showing the result of analyzing the polyacetylene film after doping with iodine bromide by differential thermal analysis (0 ° C. to 1000 ° C.) [Note that the state before doping with iodine bromide is shown in FIG. 10 (A)]. As shown in FIG. 11, even when iodine bromide is doped, the disappearance of the peak corresponding to intermolecular crosslinking and thermal decomposition (DTA peak near 300 ° C. to 500 ° C.) is observed as in the case of doping with iodine. It was seen. The results of differential thermal analysis shown in FIG. 11 confirm that even when doped with iodine bromide instead of iodine, a film-like carbon material (including graphite) having a highly retained structure of helical polyacetylene is produced. Yes. Further, the differential thermal analysis result of FIG. 11 shows that the weight loss of the helical polyacetylene due to the heat treatment can be made very small by doping with iodine bromide, and the carbon yield is increased. Yes. As in the case of doping with iodine, the film-like carbon material obtained by treating the helical polyacetylene film after doping with iodine bromide at 800 ° C. and 2600 ° C. has a high carbon yield (70 to 80%). It was also confirmed that it was obtained.

  Further, the X-ray diffraction (XRD) of the structure of the film-like carbon material (including graphite) obtained by the heat treatment at 800 ° C. and 2600 ° C. was measured. FIG. 12 (A) is a graph showing the result of measuring the carbonized material obtained by heat-treating the polyacetylene film before and after doping with iodine at 800 ° C. using an X-ray diffractometer, and FIG. It is a graph which shows the result of having measured the carbonized material obtained by heat-processing the carbonized material of FIG. 12 (A) at 2600 degreeC with the X-ray-diffraction apparatus, respectively. These XRD measurements confirmed that the 2600 ° C. heat-treated sample had high crystallinity. Specifically, as confirmed by TEM observation of a film-like carbon material obtained by heat treatment at 2600 ° C. after iodine doping, the XRD diffraction image has a graphite structure parallel to the long axis of the helical polyacetylene fibril. This is considered to support the orientation. Although not particularly shown, it was visually confirmed that the graphite structure was growing along the nanofibril from the observation with high resolution by TEM.

  As described above, in the carbonization of a helical polyacetylene film that has been controlled to a fibril structure at a nanometer size in advance, the fibrils of a helical polyacetylene film that has been controlled at a nanometer size in advance by doping iodine before carbonization. The structure could be almost completely reflected in the film-like carbon material (including graphite film) after carbonization. Therefore, since the film-like carbon material obtained in this embodiment has a highly structured fibril structure, it can be expected as a new carbon material that exhibits unknown physical properties. Practical production of a large film-like carbon material having an agglomerated structure can be expected.

  Note that since the polyacetylene film is chemically unstable in the air, it is desirable to dope iodine in an inert gas atmosphere. In addition, iodine doping may be performed by allowing the iodine gas to come into contact with the polyacetylene film for 0.5 hour or more at normal pressure and near room temperature.

  In addition, the heat treatment temperature for the carbonization may be generally 500 ° C. or higher when the polyacetylene film is carbonized. However, in the case of a polyacetylene film, it is carbonized only when the heat treatment temperature is in the range of 500 ° C. to 1000 ° C., and is structurally amorphous. When the heat treatment temperature is 1000 ° C. to 2500 ° C., graphitization proceeds as the heat treatment temperature increases as a whole, but the graphite crystal portion is nanometer-sized. Crystallization proceeds very slowly at 2500 to 3000 ° C., and tends to be in a high crystalline state as a whole. As a method of heat treatment for graphitization, carbonization is performed in the range of 500 ° C. to 1000 ° C., and then the temperature is raised or cooled to room temperature and then re-heated, and a temperature range of 2000 to 3000 ° C. You may heat-process with.

Next, the optimum range (critical significance) of the heat treatment temperature in the present invention was confirmed. Table 1 is a table showing the fibril structure and crystallinity at each heat treatment temperature for the film-like carbon material obtained in the embodiment of the present invention (iodine doping) and the other embodiment (iodine bromide doping). .

  The fibril structure and crystallinity shown in Table 1 were confirmed according to the above-mentioned conditions of SEM observation, differential thermal analysis, and X-ray diffraction analysis. In Table 1, the fibril structure was evaluated by ○ or ×. In the evaluation of the fibril structure, as a result of SEM observation and differential thermal analysis, “◯” indicates that the fibril structure constituting the helical polyacetylene film before the heat treatment is maintained, and “×” indicates that the fibril structure is not maintained. did. In Table 1, the crystallinity was evaluated with ◎, ○, Δ, and ×. In this evaluation of crystallinity, as a result of X-ray diffraction analysis, those having very high crystallinity are judged to be almost completely graphitized and evaluated as “」 ”, and those having high crystallinity are graphitized. It is judged as “O” and the crystallinity is slightly low for those with slightly low crystallinity, but some are graphitized because it is partly graphitized and “C” is low. Was determined to be not graphitized and was evaluated as “x”. In Table 1, the effect of the present invention (graphitization) was obtained not only for the evaluation of “◎” and “◯” but also for the evaluation of “Δ” (partly graphitized). Judging.

In Table 1, first, in Comparative Examples 1 to 3 in which no dopant was used, the evaluation of the fibril structure was “x”, and the fibril structure constituting the helical polyacetylene film before the heat treatment was completely broken (FIG. 13). reference). In Comparative Examples 1 to 3, since the evaluation of the fibril structure is “x”, the crystallinity is not confirmed. In Comparative Examples 4 and 5 and Comparative Examples 6 and 7, which were heat-treated at a heat treatment temperature lower than 1000 ° C. (500 ° C. and 800 ° C.) using iodine (I ₂ ) and iodine bromide (IBr) as dopants, fibrils were used. Although the evaluation of the structure was “◯”, the evaluation of crystallinity was “x” (see FIG. 7 and the like). These Comparative Examples 1 to 7 were heat-treated at 1000 ° C. to 2500 ° C. (1000 ° C., 1500 ° C., 2000 ° C. and 2500 ° C.) using iodine (I ₂ ) and iodine bromide (IBr) as dopants, respectively. In Examples 1 to 4 and Examples 5 to 8, the evaluation of the fibril structure was “◯”, and the evaluation of the crystallinity was also “Δ” or “◯” (see FIG. 8 and the like). These results indicate that when iodine (I ₂ ) and iodine bromide (IBr) are used as dopants, both are graphitized at a heat treatment temperature in the range of 1000 ° C. to 2500 ° C. As Table 1 shows, in the present invention, a critical significance is recognized in the heat treatment temperature in the range of 1000 ° C to 2500 ° C. In addition, since it confirmed that crystallization (graphitization) hardly progressed when it is higher than 2500 degreeC, in this invention, the optimal range of heat processing temperature is 1000 degreeC-2500 degreeC.

Next, the optimum range (critical significance) of the reheating temperature in the present invention was confirmed. Table 2 is a table showing the fibril structure and crystallinity at the reheat treatment temperature for the film-like carbon material obtained in the embodiment of the present invention (iodine doping) and the other embodiment (iodine bromide doping). .

  The fibril structure and crystallinity shown in Table 2 were also confirmed according to the above-described conditions of SEM observation, differential thermal analysis, and X-ray diffraction analysis. In Table 2, the evaluation of the fibril structure and the crystallinity was evaluated by the same method as in Table 1 above. In Table 2, unlike the case of Table 1, with respect to the evaluation of “Δ” (only a part of the graphitization could be confirmed), the effect of the present invention (advanced graphitization) was not obtained. Deciding.

In Table 2, in Comparative Examples 8 and 9 where heat treatment was performed at a heat treatment temperature of 1500 ° C. using iodine (I ₂ ) and iodine bromide (IBr) as dopants, the evaluation of the fibril structure was “◯”. The evaluation of sex was “△”. On the other hand, Examples 9-11 and Example 12 heat-treated at 2000 ° C. to 3000 ° C. (2000 ° C., 2600 ° C. and 3000 ° C.) using iodine (I ₂ ) and iodine bromide (IBr) as dopants, respectively. In ˜14, the evaluation of the fibril structure was “◯”, and the evaluation of the crystallinity was “◯” or “」 ”. These results indicate that when iodine (I ₂ ) and iodine bromide (IBr) are used as dopants, both are graphitized at a reheat treatment temperature range of 2000 ° C. to 3000 ° C. Table 2 shows that when reheat treatment is performed at 2000 ° C. to 3000 ° C., the graphite is highly advanced in terms of shortening the heat treatment time and the like, compared with the case of heat treatment at a heat treatment temperature of 1000 ° C. to 2500 ° C. shown in Table 1. There was a tendency to make it easier. As shown in Table 2, in the present invention, the critical significance is recognized in the reheat treatment in the range of 2000 ° C to 3000 ° C. In addition, since it confirmed that crystallization (graphitization) hardly progressed when it was higher than 3000 degreeC, in this invention, the optimal range of heat processing temperature is 2000 degreeC-3000 degreeC.

It is a structural formula of the polyacetylene molecule | numerator which comprises the polyacetylene film used by embodiment of this invention. (A) is a photograph of a part of a chiral nematic liquid crystal (N * -LC) taken with a polarizing microscope, and (B) is a chiral nematic constructed based on the chiral nematic liquid crystal (N * -LC) of (A). It is the photograph which image | photographed the liquid crystal reaction field with the scanning electron microscope (SEM). (A) is a photograph taken by SEM of the domain structure of a helical polyacetylene film synthesized in the chiral nematic liquid crystal reaction field of FIG. 2 (B), and (B) is a photograph of the domain structure of the helical polyethylene of (A). It is the photograph which image | photographed one part by SEM. It is the photograph which image | photographed a part of domain structure of a horizontal orientation type polyacetylene film by SEM. It is the photograph which image | photographed a part of domain structure of a vertical alignment type polyacetylene film by SEM. It is the photograph which image | photographed a part of domain structure of an oriented helical type polyacetylene film by SEM. (A) is a photograph taken by SEM of part of the domain structure of a film-like carbon material obtained by heat-treating a polyacetylene film doped with iodine according to an embodiment of the present invention at 800 ° C. FIG. 4 is an enlarged photograph obtained by enlarging a part of the domain structure of the film-like carbon material of FIG. (A) is the photograph which image | photographed the domain structure of the film-form carbon material obtained by heat-processing the film-form carbon material of FIG. 7 (A) further at 2600 degreeC by SEM, (B) is the film of (A) It is the enlarged photograph which expanded and image | photographed the domain structure of glassy carbon material by SEM. It is the photograph which image | photographed a part of domain structure of the film-form carbon material obtained by heat-processing the polyacetylene film which doped iodine bromide which is other embodiment of this invention at 800 degreeC by SEM. (A) is a graph showing the results of analyzing the polyacetylene film before doping with iodine by differential thermal analysis, (B) is a graph showing the results of analyzing the polyacetylene film after doping with iodine by differential thermal analysis. is there. It is a graph which shows the result of having analyzed the polyacetylene film after doping iodine bromide by differential thermal analysis. (A) is a graph which shows the result of having measured the carbonized material obtained by heat-treating the polyacetylene film before and after doping with iodine at 800 ° C. with an X-ray diffractometer (XRD). It is a graph which shows the result of having measured the carbonized material obtained by heat-processing the carbonized material of A) further at 2600 degreeC with the X-ray-diffraction apparatus (XRD). (A) is a photograph of part of the domain structure of an iodine-undoped oriented helical polyacetylene film taken by SEM, and (B) is a heat treatment of the iodine-undoped helical polyacetylene film of (A) at 400 ° C. (C) is a photograph taken by SEM of a state in which the iodine-undoped polyacetylene film of (A) was heat-treated at 450 ° C.

Claims (8)

Doping iodine as an electron acceptor on a polyacetylene film composed of aggregated fibrils having an average fiber diameter of nanometer level,
By using the polyacetylene film doped with iodine as a precursor and carbonizing at a heat treatment temperature of 1000 ° C. to 2500 ° C. in an inert gas atmosphere, it has an average fiber diameter of nanometer level maintaining the shape of the precursor A method for producing a film-like carbon material constituted by agglomeration of graphitized carbon fibrils. Doping iodine as an electron acceptor on a polyacetylene film composed of aggregated fibrils having an average fiber diameter of nanometer level,
Using the polyacetylene film doped with iodine as a precursor, carbonized at a heat treatment temperature of 500 ° C. or higher in an inert gas atmosphere to aggregate carbon fibrils having an average fiber diameter of nanometer level maintaining the shape of the precursor Make a carbon material in the form of a film,
After returning the film-shaped carbon material to room temperature, it is reheat-treated at a temperature of 2000 ° C. to 3000 ° C., whereby the graphitized carbon fibrils having an average fiber diameter of nanometer level are aggregated to form a film shape A method for producing a carbon material. Doping iodine bromide as an electron acceptor on a polyacetylene film composed of aggregated fibrils having an average fiber diameter of nanometer level,
Using the polyacetylene film doped with iodine bromide as a precursor, carbonization is performed at a heat treatment temperature of 1000 ° C. to 2500 ° C. in an inert gas atmosphere, thereby maintaining a nanometer-level average fiber diameter that maintains the shape of the precursor A method for producing a film-like carbon material constituted by agglomeration of graphitized carbon fibrils having the following structure. Doping iodine bromide as an electron acceptor on a polyacetylene film composed of aggregated fibrils having an average fiber diameter of nanometer level,
Carbon fibrils having an average fiber diameter of nanometer level in which the polyacetylene film doped with iodine bromide is carbonized at a heat treatment temperature of 500 ° C. or more in an inert gas atmosphere and the shape of the precursor is maintained. Made a film-shaped carbon material composed of
After returning the film-shaped carbon material to room temperature, it is reheat-treated at a temperature of 2000 ° C. to 3000 ° C., whereby the graphitized carbon fibrils having an average fiber diameter of nanometer level are aggregated to form a film shape A method for producing a carbon material.   The method for producing a film-like carbon material according to claim 1, 2, 3, or 4, wherein the precursor has a shape formed by agglomerating fibrils having an average fiber diameter of nanometer level. Graphite is produced by carbonizing a polyacetylene film formed by agglomerating fibrils having an average fiber diameter of nanometer level, doped with iodine or iodine bromide as an electron acceptor, and maintaining the shape of the fibrils. A film-like carbon material composed of aggregated carbon fibrils.   The film-like carbon material according to claim 6, wherein the polyacetylene film has a structure in which fibrils having an average fiber diameter of nanometer level are oriented and aggregated in a specific direction.   The film-like carbon material according to claim 6, wherein the polyacetylene film has a structure in which a large number of portions formed by swirling fibrils having an average fiber diameter of nanometer level are aggregated.